A jury in Texas finds Eddie Ray Routh guilty of murdering Chris Kyle, the former U.S. Navy SEAL whose autobiography was turned into the hit movie "American Sniper." (Reuters)

Eddie Ray Routh, the man who killed “American Sniper” Chris Kyle and his friend in a rifle range rampage, will spend the rest of his life in prison.

Routh, 27, was convicted Tuesday night of first-degree murder in the Feb. 2, 2013, killings of former Navy SEAL Kyle, 38, and Chad Littlefield, 35. The case drew international attention, and unfolded as the bestselling memoir by Kyle, often called the most deadly sniper in U.S. military history, was made into a blockbuster movie that has grossed more than $300 million.

The trial in Stephenville, Tex., centered on whether Routh should be held responsible despite being diagnosed in recent years with psychosis, schizophrenia and other mental illnesses. His lawyers argued he should be found not guilty by reason of mental insanity, while prosecutors said that his conditions were no excuse for murder.

The jury of two men and 10 women found Routh guilty with a unanimous vote in the Erath County District Court, about 90 miles southwest of Dallas. Erath County District Court Judge Jason Cashon sentenced him to life in prison without the possibility of parole. It was a capital case, but prosecutors took the death penalty off the table before the trial started.

Littlefield’s mother, Judy, told media outside the courthouse after the verdict was read that her family had waited two years for justice, and credited God for the outcome. She also thanked reporters for their compassion in the case.

“We’re so thrilled that we have the verdict that we have tonight,” she said.

Court officers told the media that no additional statements would be made Tuesday night. Supporters of the Kyle and Littlefield families in the courtroom included Jay Novacek, a former football player with the Dallas Cowboys, and Marcus Luttrell, a Navy SEAL veteran whose story was depicted in the 2013 movie “Lone Survivor.”

As outlined in this front-page story for The Washington Post written from Stephenville earlier this month, Kyle and Littlefield were killed after Routh’s mother had asked the Navy SEAL veteran to help her son with post-traumatic stress. They picked him up in Kyle’s massive Ford F-350 pickup truck the day of the killings with plans to bond with Routh over a shared hobby, shooting, and offer some ways to help.

The trio drove about 90 miles southwest to the Rough Creek Lodge and Resort, a luxury facility with a rifle range that Kyle had helped design and used frequently with his military training company, Craft International. They arrived at 3:15 p.m., and about 90 minutes after, they were found dead by a resort employee.

Kyle, a father of two, was shot six times with one of his own .45-caliber pistols, including a “rapidly fatal” wound to the back that pierced his aorta and another to the jaw that caused a lethal spinal cord injury. Littlefield, a father of one, was hit seven times, including four that would have been instantly fatal, according to court testimony. Routh used a 9mm Sig Sauer handgun, owned by Kyle and engraved with the Navy’s anchor symbol, to kill Littlefield, and then took it with him.

Routh fled the scene in Kyle’s pickup truck, and was eventually pursued by police in his hometown of Lancaster, Tex., south of Dallas. His sister, Laura Blevins, had called the police after he visited her and said that he had killed two men.

Routh initially had a tense 30-minute standoff with police outside his home in which he refused to get out of the truck and asked “is this about hell walking on Earth right now?” He eventually led them through a series of residential neighborhoods at speeds of up to 100 mph in Kyle’s truck, and was rammed by a police cruiser. He continued on for several more minutes, until the truck became incapacitated as fluids poured out.

It’s unclear how much Kyle and Littlefield knew about Routh’s mental instability. While he had been diagnosed with post-traumatic stress, his military record shows that he did not see direct ground combat. He had been released from psychiatric treatment about a week before meeting Kyle and Littlefield for the first and last time.